George Romney is chosen as Nixon's Vice President in 1968, they win against Humphrey in the general. As Romney is clean of scandal, he isn't forced to resign like Agnew was in 1973. In this, McGovern faces a battle for the Democratic nomination in 1972 from Henry Jackson; splitting the party. To this extent, Watergate never happens as Nixon is confident of re-election. Nixon/Romney are re-elected and Nixon does not resign in 1974, going on to serve out his term until 1977.
Romney faces Reagan in the 1976 GOP primary while Jackson storms into the Democratic lead, finally Henry Jackson is nominated for the Democrats with his opponent being Ronald Reagan. A bitter, bloody campaign follows where the Republicans take control of the House but lose the White House to Jackson. President Jackson has major successes in the areas of job creation, energy, urban redevelopment and foreign policy where he works with the Republicans but a Christian wing, led by Reagan with major influence in Congress blocks his plans for the economy, health and education, effectively holding Jackson hostage. With a poor economy, Jackson is defeated in the 1980 election by a resurgent Reagan.
Reagan becomes President in 1981 with a strongly conservative Congress, the economy improves in late 1982 but in December of that year, he is shot by John Hinckley Jr., a former government worker in Los Angeles (butterflies ensure the 1981 attempt is delayed as President Jackson's job creation efforts ensured Hinckley Jr. had a stable income as a govt. worker till Reagan's policies cut his job). The injury is much more serious ITL and the Cabinet led by Secretary of State Al Haig (who wants the Presidency at a later date) convinces the weak-willed Vice President Howard Baker to invoke the 25th Amendment, thus Baker is sworn in as President on December 17th 1982.
Reagan recovers from his injury while plotting to replace Baker in 1984, in similar conditions, former President Jackson who has become a beacon for moderates and liberals following blatant gerrymandering and partisanship from the Christian GOP wing of Congress plans another bid. Baker, a well-intentioned man narrowly enacts a far more moderate domestic and foreign policy agenda than Reagan with support of GOP moderates and the Democrats, with a good economy he is expected to get the nomination in 1984 until Reagan announces he intends to and as such Baker is cut off by the GOP leaving him as a lame-duck, Jackson gets the DNC nomination for a third time as does Reagan.